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March 23, 2009

Squeege Life Span

Is there a recommended or standard usage rate for stencils?

Should I expect different usage rates for metal, rubber or plastic?

Is there a specific way to determine when it's time to replace a squeege?



S.T.

Experts Comments

Is there a recommended or standard usage rate for stencils?
With a properly tuned stencil printer and good quality squeegee blades, one should expect 500,000+ prints from a metal stencil.

Should I expect different usage rates for metal, rubber or plastic?
Yes.Metal squeegee blades have a much longer life compared to rubber or plastic.Metal squeegee blades are the most durable.Plastic blades have the next higher usage rate and the lowest is when usingrubber squeegee blades.

Is there a specific way to determine when it's time to replace a squeegee?
Most customersreplacemetal squeegee blades when the blades are damaged.For plastic blades, a typical life is approximately 40,000 prints on each edge.For rubber, the life drops to approximately 20,000 prints.The higher the pressure on the squeegee blade, the shorter the useful life.

Robert Dervaes
V.P. Technology & Engineering
Fine Line Stencil, Inc.
Robert Dervaes has worked in the electronics industry since 1992 in both design and manufacturing. Over the past 11 years he has established the technical foundation of Fine Line Stencil, Inc. - a premier stencil supplier to the electronics industry.

Is there a recommended or standard usage rate for stencils?
Most stencils are made of Stainless steel, and these have alifespan whichranges from 300,000 cycles to 800,000 cycles. Handling damage andsetup flatness and protrusions are the key elements that affect stencil life.

Should I expect different usage rates for metal, rubber or plastic?
Yes. Rubber and Plastic "coin" stencils by local deformation at pcb edges, rail edges and inrouted recesses on the pcb. They also wear out fast because of their low shear strength. Rubber squeegees can have a life span of 1-week to 3-months depending on a users tolerance to printing variation. Metal squeegee lifespan can range from 3months for softstainless steel metal, to 18months for spring steel blades. Metal squeegees will impart less wear and damage to stencils because they do not locally deform and coin the stencil.

Is there a specific way to determine when it's time to replace a squeegee? Squeegee life and quality should be discussed with all your process engineers and operations and a "standard" should be established. We do not recommend rubber or plastic squeegees because of their wide variation in performance and lack of edge quality.

With softer Stainless Steel Metal squeegees, extra care must be taken to avoid dings and dents from handling. We recommend all squeegee be inspected before installation, and discarded if they contain any edge flaws such as nicks or dents. For harder Spring Steel blades, they are less likely to experience dings and they should be inspected after 6-months, every 30 days thereafter. Again, the criteria should be edge quality (continuous smooth edge, no nicks or dents).

All operators and process engineers should flag and stop any printer / squeegee setup which is not wiping properly. This is an indication of a squeegee or printer setup problem. The swipe of the squeegee should produce a smooth shiny stencil surface with no puddles or streaksof solder paste left behind. Squeegee Pressure should be set to minimum to produce a clean wipe, plus 10% extra.

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Mark J. Curtin
President
Transition Automation, Inc.
Mr. Curtin is the founder and president of Transition Automation, Inc. Their main product is Permalex Edge Metal Squeegees. They also sell the PrinTEK Ultra-Fine Pitch stencil printers. His background includes 25 years of designing squeegees and SMT printers. He is closely familiar with the SMT printing process, squeegee design, and all aspects of in-line printing machines, double-sided tooling, stencils and solder paste performance.
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